fix panic on overflowing ascii85 decode #233
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Found this bug while fuzzing the crate The range of values that an ascii85 character can take is slightly bigger than what fits in a u32. If a, b, c, d, and e are very high, the multiplication will result in a number that cannot be represented as a u32. This should be considered as a decoding error, but the code didn't check for this case and panicked. Do the computation in a u64 instead, and try to cast it to a u32 at the very end, returning None if the value is invalid.
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Found this bug while fuzzing the crate
The range of values that an ascii85 character can take is slightly bigger than what fits in a u32. If
a,b,c,d, andeare very high, the multiplication will result in a number that cannot be represented as a u32. This should be considered as a decoding error, but the code didn't check for this case and panicked.Do the computation in a u64 instead, and try to cast it to a u32 at the very end, returning None if the value is invalid.